The present invention relates to a torque wrench for applying torque to fasteners.
Torque wrenches are well known in the art. Typically, a torque wrench includes a fastener drive structure having a fastener engaging head, such as a ratchet-type head, and an elongated tang member extending from the head. The fastener drive structure is inserted within a casing structure. The fastener drive structure and the casing structure are pivotally connected by a pivot pin for relative pivotal movement between a normal position and a torque exceeded position. A tang engaging member is biased by a spring into engagement with a rear end portion of the tang member to maintain the fastener drive structure and the casing structure in the normal position during a torque applying operation. An adjuster is provided to adjust the stress in the spring. During the application of torque to the fastener, the spring maintains the fastener drive structure and the casing structure in the normal position until the torsional resistance offered by the fastener reaches a threshold level determined by the spring force. Upon reaching that torsional resistance, the manual force being applied to the casing structure pivots the casing structure relative to the fastener drive structure, thereby causing the casing structure to contact the fastener drive structure to create an audible xe2x80x9cclick.xe2x80x9d This xe2x80x9cclickxe2x80x9d indicates to the user that the threshold level of torque has been reached.
One shortcoming of these types of torque wrenches is that wear at the pivotal connection between the fastener drive structure and the casing structure allows the fastener drive structure to xe2x80x9cwobblexe2x80x9d relative to one another about the pivot pin. By this wobbling movement, the rear end portion of the tang member can become displaced relative to the tang engaging member in the direction perpendicular to its normal direction of movement. This can lead to inconsistencies in operation of the wrench.
Consequently, there exists a need for a torque wrench wherein the stability of the fastener drive structure is improved.
To meet the above-described need, the present invention provides a torque wrench for applying torque to fasteners constructed in accordance with the principles of the present invention. The torque wrench comprises a fastener drive structure having a head which is constructed and arranged to be removably engaged with a fastener and a tang structure extending rearwardly from the head. A wrench body includes a casing structure. The fastener drive structure and the casing structure are pivotally connected for pivotal movement relative to one another from a normal position to a torque exceeded position to generate a torque exceeded signal.
A tang engaging and stabilizing structure has a tang engaging portion and a pair of stabilizing ear members spaced apart from one another in the direction of the pivot axis. The stabilizing ear members are positioned on opposing sides of a rear end portion of the tang structure to restrict movement of the tang structure rear end portion generally in the direction of the pivot axis. The tang engaging portion is engaged with a rear end portion of the tang structure when the fastener drive structure is in the normal position thereof. A stressed biasing element applies a biasing force to the tang engaging and stabilizing structure to maintain the tang engaging portion in engagement with the rear end portion of the tang structure. During a torque applying operation, a force applied to the wrench body is transmitted as torque to a fastener removably engaged with the head and tends to pivot the casing structure relative to the fastener drive structure about the pivot axis. The biasing force applied by the biasing element maintains the tang engaging portion in engagement with the tang structure rear end portion so as to maintain the casing structure and the fastener drive structure in the normal position. When a torsical resistance offered by the fastener reaches a threshold level determined by the biasing force of the biasing element, the force being applied to the wrench body then pivots the casing structure relative to the fastener drive structure to the torque exceeded position to generate the torque exceeded signal. Thus, the signal indicates that the torsional resistance being offered by the fastener has reached the threshold level. An adjuster is constructed and arranged such that movement thereof adjusts the stress in the biasing element and hence the biasing force applied to the tang engaging portion so as to set the aforesaid threshold level of torsional resistance at which the force being applied to the wrench body pivots the casing structure relative to the fastener drive structure as aforesaid.
Other objects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, the principles of this invention.